Instead of simply spiking the flange of a railroad rail to a railroad tie, it is now considered better practice in at least high-stress locations such as curves to secure the rail via a rail-fastening plate and blots to the railroad tie. To this end there is provided at each tie under the rail a so-called saddle or rail-fastening plate having ridges that closely flank the flange of the rail. These fastening plates, which constitute with the ties supports for the rails, are normally permanently spiked into the ties. Bolts and rail clips then secure the flanges of the rails to these plates, so that exact and secure positioning of the rails on the rail-fastening plates is insured. To this end each of the plates is normally provided at its ridges with upwardly open notches that are dimensioned so that the heads of the bolts can simply be slipped laterally into them, but so that the bolts cannot be pulled vertically out.
In the simplest systems the bolt is provided with a washer that overreaches the edge of the flange to secure same tightly to the fastening plate. Although the system has the considerable advantage of simplicity, it does have the disadvantage that the enormous stresses exerted on the bolt fastening can often lead to its loosening, as there is virtually no possibility for displacement of the rail relative to the plate without damage to or loosening of the bolt fastening.
To this end the above-mentioned clips are provided on the heads of the bolts, such as described in German Pat. Nos. 1,053,016, 1,126,901, and 1,246,005. Such systems incorporate springs between the bolt and the rail flange, so that a tensioning force of approximately 1200 daN is achieved with a relative displacement of approximately 15 mm. Such systems nonetheless are typically relatively difficult to assemble, e.g. requiring the use of special tools. In particular torquing the bolt down for the desired spring force requires particular equipment and expert labor.
It is also known from German Pat. Nos. 1,261,151 and 1,954,008 (whose U.S. equivalent is U.S. Pat. No. 3,690,551) to use a W-shaped clip. The central loop of this clip is formed into an eye through which the bolt passes. The two flanking loops are bent down and act as support feet that bear on the fastening plate. The ends of the W-shaped clip are bent down and in and bear resiliently on the edge of the flange. As the portions of the W-shaped clip embrace the ridge of the fastening plate, the tendency for the clip to twist when the bolt is tightened is somewhat reduced.
The disadvantage of this last-described system is that it is relatively difficult to obtain the desired spring force uniformly with a multiplicity of such fasteners. The bolts must be meticulously torqued, and even so the spring force only remains relatively uniform over a very small spring displacement. What is more the reliance almost completely on bending stresses for the spring force results in quick fatigue of the unit, while at the same time the clip must be relatively heavily dimensioned to obtain the required relatively large spring force.